The present invention relates to a process for production of starch sugar and more particularly to a process for production of starch sugar which comprises introducing liquefied starch into a reactor filled with various amylases immobilized onto porous chitosan, to thereby convert the starch into the corresponding starch sugar such as glucose, maltose and maltooligosaccharides.
Furthermore the present invention relates to immobilized debranching enzyme and more particularly to debranching enzyme immobilized onto a specific support which is to be used in the production of various starch sugars. This debranching enzyme, when used in combination with various immobilized amylases, permits production in high yield of starch sugar such as glucose, maltose and maltooligosaccharides from liquefied starch.
Various methods for producing starch sugar utilizing immobilized enzyme have been proposed. For example, a method for producing a high concentration of glucose, employing immobilized glucoamylase is disclosed in Japanese Patent Publication No. 17517/1982, Japanese Patent Application Laid-Open No. 60989/1983, etc. The method disclosed in Japanese Patent Publication No. 17517/1982, however, has a disadvantage in that the concentration of glucose is insufficiently low. In accordance with the method disclosed in Japanese Patent Application Laid-Open No. 60989/1983, a high concentration of glucose can be produced from potato starch as the starting material. However, there is no description about the use as the starting material of corn starch and the like from which a high concentration of glucose is generally difficult to produce.
Immobilization of .beta.-amylase and production of maltose employing the immobilized .beta.-amylase are disclosed in Japanese Patent Application Laid-Open No. 198977/1984, etc. In this immobilized .beta.-amylase, it is desired to more improve the stability of enzyme activity
The present inventors have developed a method for producing maltooligosaccharide by immobilizing amylase which is able to produce maltooligosaccharide having a higher degree of polymerization than maltose Although this method is sufficiently suitable for practical use, it is desirable to more efficiently utilize expensive enzyme.
As a result of extensive investigations on a support on which amylase is immobilized, it has been found that the liquid flow rate can be increased in comparison with the prior art method and further that enzyme activity can be improved more stably. It has further been found that the yield of the desired starch sugar can be increased by employing a dual enzyme system including two kinds of immobilized enzymes in combination.